Concentrated solutions of auramine dyes



I United States Patent Ofifice 3,3M,994 Patented Apr. 18, 1967CQNCENTRATED SOLUTHUNS F AURNE EYES Fritz Schubert and Eberhard Lueclre,Ludwigshafen (Rhine), Germany, assignors to Badische Altllllll: 8cSoda-Fahrilr Alttiengesellschaft, Ludwigshafen (Rhine), Germany NoDrawing. Filed Dec. 3, 1963, Ser. No. 327,834 Claims priority,application Germany, Dec. 7, 1962, 13 69,895; Dec. 118, 1962, R 70,021 6Claims. (Cl. 260-566) This invention relates to highly concentratedsolutions of salts of auramine with sulfuric acid or its acidwatersoluble derivatives.

Auramine dyes are used on a large scale in the form of their aqueoussolutions in the paper industry. In general the dyes are used in finelyground form for the preparation of the said solutions. The use ofpowdered dyes however has considerable disadvantages. Thus for exampleit is diflicult to dissolve the dyes if the finely ground dry powder haspartly or completely agglomerated into lumps by the action of moistureor heat owing to unsuitable storage. Moreover the weighing out, transferor feeding of powdered Water-soluble dyes having very high tinctorialstrength is accompanied by unpleasant dust formation. When the dyes aredissolved and when the solutions are stirred, particularly duringincorporation into the paper pulp, there is frequently marked frothformation leading to frothing over of the solutions and consequentcontamination and waste.

To avoid dusting of the finely ground dyes and frothing during thepreparation or stirring of solutions it has been proposed to add certainsubstances. Many wetting agents have also been recommended for promotingrapid and complete solution of dye powders. These additives are Withoutexception auxiliaries which lessen the said dis advantages withoutcompletely obviating them.

The disadvantages of finely ground auramines in industrial use may beavoided by the use of highly concentrated stock solutions supplied bythe dye manufacturer. Highly concentrated aqueous solutions couldhowever not be prepared hitherto.

Auramines have hitherto usually been prepared in the form of theirchlorides. These have relatively poor solubility in water (only about1%) and even these solutions deposit dye upon prolonged standing.Furthermore the auramines readily hydrolyze in Michlers ketone uponprolonged heating in aqueous solution or in an acid medium.

It is the object of the present invention to provide stable concentratedsolutions of auramine dyes which do not have the said disadvantages.

This object is achieved by the concentrated solutions according to theinvention which contain salts of bases of auramines with sulfuric acidor its acid, water-soluble derivatives in any water-miscible solventwhich is liquid at room temperature and has a boiling point (atatmospheric pressure) of more than 80 C. or preferably of more than 100C.

Suitable auramine dyes are for example salts of Auramine 0 Base (ColourIndex, 2nd edition, No. 41,000B) or Auramine G Base (Colour Index, No.41,005).

Examples of water-soluble solvents having a boiling point of more than80 C., particularly of more than 100 C., which are liquid at roomtemperature are monohydric or polyhydric alcohols, such as ethyleneglycol, butanediol, diethylene glycol, thiodiglycol, triethylene glycol,dipropylene glycol, their others, such as diethylene glycol methyl etheror diethylene glycol butyl ether, watersoluble polyethers, such as thepolymerization products of alkylene oxides Whose terminal groups may beesterified or etherified, lactones, such as butyrolactone, amides, suchas formamide, dimethylformamide or N-methylpyrrolidone, and alsoacetonitrile, pyridine and dimethyl sulfoxide or mixtures of the saidsolvents. These solvents need not be anhydrous, but may contain water.

Among the said solvents, formamide is particularly suitable for thepreparation of stable solutions. A solution of Auramine O sulfate informzamide is particularly advantageous industrially.

The concentrated solutions contain the salts af auramine bases withsulfuric acid or its derivatives to the extent of about 20 to about 60%,preferably 30 to 50% by weight with reference to the weight of thesolution.

The solutions may be more dilute, but such dilution is not advantageousowing to increased costs for solvent and transportation.

The solutions according to this invention may also contain othersolvents which are miscible with water and which boil at less than C.

Examples of suitable acid, water-soluble derivatives of sulfuric acidare aminosulfonic acids, chlorosulfonic acid or the methyl or ethylesters of sulfuric acid. For the production of sulfates it is preferableto use the acid, water-soluble derivatives of sulfuric acid, such assodium, potassium or ammonium bisulfate.

The procedure for the preparation of the solutions according to thisinvention may be for example that the auramine base is dissolved in anon-polar solvent which is not miscible with the water-miscible solvent,such as chloroform, ethylene chloride, trichloroethylene,dichlorobutane, benzene, toluene or xylene, and that the stoichiometricamount of sulfuric acid or an acid salt or acid derivative thereof isadded to the solution obtained. A deficiency of the acid component, forexample a deficiency of 10 to 30%, is however often sufficient. Sulfuricacid monohydrate or an equivalent amount of oleum may also be usedinstead of sulfuric acid. The reaction is over within a short time. Thesolvent miscible with water is then added and the dye dissolved therein.The dye solution is then separated. In some cases it is advantageous toadd to the mixture basic substances, such as urea, bis-4,4dimethylaminodiphenylmethane, ethanolamine or diethanolamine, inorder to achieve more eflicient separation of the layers. If desired,non-polar solvent still contained in the dye solution, such aschloroform or benzene, may readily be removed by treatment undersubatmospheric pressure or by blowing in air or nitrogen.

The separated non-polar solvent may be purified by distillation with orwithout steam. The residue remaining may readily be converted intoMichlers ketone.

The solutions according to this invention may also be prepared byreacting the auramine bases with sulfuric acid or its derivatives inorganic solvents which are miscible with water. For this purpose, forexample, the auramine base is suspended in a solvent or mixture ofsolvents and a solution of sulfuric acid or derivative there of in thesame or another solvent is allowed to flow into this suspension slowly.After stirring the reaction mixture for some time, undissolvedconstituents are filtered off and a concentrated auramine solution isobtained.

It is also possible for example to dissolve the sulfuric acid in asolvent such as formamide and to add the mix- Example 1 268 parts ofAuramine 0 Base (Colour Index No.

41,000B) is dissolved in 1340 parts of chloroform at room :mperature. Asolution of 44 parts of concentrated llfuric acid in 565 parts offormamide is allowed to flow ltO the filtered solution while stirring inthe course of fteen minutes, the temperature rising from 30 to 37 C. 5parts of bis-4,4-di-methylaminodiphenylmethane is 1en added in smallportions and the mixture is stirred for venty minutes. The chloroform isseparated and then re chloroform still contained in the dye solution isdislled off under subatmospheric pressure. 773 parts of an uraminesolution is obtained which contains about 36% y weight of dye. Thisauramine solution may be diluted 1 all proportions with water and usedfor the production f aqueous dye liquors.

The chloroform solution separated may be distilled and 1e residue may behydrolyzed without difficulty to Iichlers ketone.

Example 2 134 parts of Auramine Base is dissolved in 650 parts ftoluene. A solution of 22 parts of concentrated suluric acid in 160parts of formamide is allowed to flow nto the filtered solution in thecourse of twenty minutes vhile stirring. The temperature rises from 32to 40 C. .he whole is further stirred for about twenty minutes and henthe toluene is separated off. Toluene residues still ontained in the dyesolution are removed by heating tnder subatmospheric pressure. 300 partsof a brown .ye solution is obtained which contains 49.5% of dye. ."heconcentrated solution may readily be diluted with vater.

The toluene may for the most part be recovered from he separated toluenesolution by distillation or by extelling it with steam. The residue maythen readily be rydrolyzed to Michlers ketone.

Trichloroethylene may be used instead of toluene. The ulfuric acid maybe replaced by an equivalent amount if 26% oleum.

Example 3 134 parts of Auramine 0 Base is dissolved in 82 parts Ifpropanol at 50 to 55 C. 49 parts of concentrated .ulfuric acid isallowed to flow in within half an hour at he same temperature. Shortlyafter the end of the addiion, an orange crystalline product isprecipitated. The vhole is stirred for about another twenty minutes andhe dye then suction filtered. The hydrogen sulfate is vashed twice withacetone and dried under subatmosnheric pressure. The yield is 141 partsof dye (melting goint 216 to 221 C.). V

The dye is dissolved in dipropylene glycol, formamide 31dimethylformamide in the ratio 1:1. A 50% dye soluion is thus obtainedwhich may be diluted With water :0 a clear solution.

Example 4 134 parts of Auramine 0 Base is suspended in 280 parts 3fformamide by stirring. 57 parts of sodium bisulfate is added to thesuspension. The temperature rises from 24 to 46 C. The mixture isstirred overnight at room temperature, another 6 parts of sodiumbisulfate is added, stirring continued for some time and the whole thenfiltered. 359 parts of a dark auramine solution is thus obtained havinga dye content of 40.0%; it may be diluted to any desired extent to forma dye liquor.

Equivalent amounts of potassium bisulfate or ammonium bisulfate may beused instead of sodium bisulfate.

Example 134 parts of Auramine 0 Base is suspended in 225 parts offormamide in a ball mill. A solution of 24.5 parts of concentratedsulfuric acid in 55 parts of formarni'de is allowed to flow slowly intothe mixture while stirring. The mixture is then treated for 4 /2 hoursin a ball mill and the brown auramine solution formed is then filteredfree from undissolved constituents. 367 parts of a dark auraminesolution is obtained which contains 35.5% by weight of dye. The solutionis capable of unlimited dilution with water.

Sulfuric acid monohydrate may be used instead of concentrated sulfuricacid.

The filter residue may easily be hydrolyzed to Michlers ketone.

Example 6 Example 7 402 parts of Auramine 0 Base is dissolved in 1900parts of chloroform and while stirring at room temperature 171 parts ofsodium hydrogen sulfate is introduced. A rise in temperature from 24 to36 C. takes place. The reaction mixture is stirred for another twentyminutes and then filtered. The filtrate is allowed to flow into 2700parts of benzene while cooling, the dye thus being deposited incrystalline form. The residue is suction filtered after having beenstirred for a short time. 476 parts of a yellow auramine dye isobtained. When Auramine G Base is used instead of Auramine 0 Base, a dyewith similar properties is obtained.

A concentrated, for example 40%, stable solution can be prepared bydissolving the dyes thus obtained in formamide.

We claim:

1. A concentrated solution containing from about 20 to about 60% byweight of a dye of the formula AX where A represents the cation of anauramine selected from the class consisting of Auramine O and Auramine Gand X represents an anion selected from the class consisting of S0 50 11NH SO (3150 CH OSO and C I-l -OSO in an inert organic solvent which ismiscible with water in all proportions, which is liquid at normaltemperature and which has a boiling point above C.

2. The concentrated solution as claimed in claim 1 in which theconcentration of said dye is about 30 to 50% by Weight.

3. The concentrated solution as claimed in claim 1 which has beendiluted with Water.

4. A concentrated solution containing from about 20 to about 60% byweight of a dye of the formula A X where A represents the cation of anauramine selected from the class consisting of Auramine O and Auramine Gand X represents an anion selected from the class consisting of S0469,SOLLHG, NH2SO ClSO3 CHgOSOg and C H -OSO in a solvent selected from theclass conisting of glycol, butanediol, diethyleneglycol,diethyleneglycolmethvl ether, diethyleneglycolbutyl ether,butyrolactone, formamide, dimethylformamide, N-methylpyrrolidone,acetonitrile, pyridine and dimethylsulfoxide.

5. A concentrated solution containing from about 20 to about 60% byweight of Auramine O sulfate in formamide.

6. A concentrated solution containing from about 20 to about 60% byweight of Auramine 0 hydrogen sulfate in formamide.

References Cited by the Examiner UNITED STATES PATENTS 3,209,027 9/1965Grosklos 260-566 CHARLES B. PARKER, Primary Examiner.

FLOYD D. HIGEL, Assistant Examiner.

1. A CONCENTRATED SOLUTION CONTAINING FROM ABOUT 20 TO ABOUT 60% BYWEIGHT OF A DYE OF THE FORMULA A$X$ WHERE A$ REPRESENTS THE CATION OF ANAURAMINE SELECTED FROM THE CLASS CONSISTING OF AURAMINE O AND AURAMINE GAND X$ REPRESENTS AN ANION SELECTED FROM THE CLASS CONSISTING OF SO4$$,SO4H$, NH2SO3$, CISO2$, CH3OSO3$ AND C2H5-OSO3$, IN AN INERT ORGANICSOLVENT WHICH IS MISCIBLE WITH WATER IN ALL PROPORTIONS, WHICH IS LIQUIDAT NORMAL TEMPERATURE AND WHICH HAS A BOILING POINT ABOVE 80*C.